Note: Descriptions are shown in the official language in which they were submitted.
2a 63888
The present invention generally relates to
refrigeration compressors and, more particularly,
to such compressors having an orbiting piston
member, wherein it is possible to provide an axial
and radial compliance force on the orbiting piston
member to bias it toward the compressor cylinder
walls for proper sealing.
~ typical rotary compressor coa~rises a
rotating piston member or roller and a cylinder
housing, wherein the rotation of the roller
compresus refrigerant fluid. Rotary compressors
have advantages over other types of compressors by
virtue of their high efficiency, small size, and
low cost. Disadvantages of rotary co~ressors lie
in the necessity of close tolerances between the
piston and cylinder walls and the high costs of
manufacturing parts with. such close tolerances.
Scroll compressors employ two opposing
2o involutsswon~ stationary and one orbiting to
compress fluid. The sealing mechanism of scroll
type compressors includes structures for axial and
radial compliance of the scroll members. An
advantage of scroll compressors over rotary
compressors is that friction between moving parts
is decreased since the scrolls are not rotating.
Particular disadvantages of scroll c,Qnpressors are
the long machining times for end milling the
scroll wraps and the requiramertt for very close
tolerances between the scroll wraps. These
requirements make the scrolls vary expensive to
manufacture. An example of a scroll compressor is
found in U.S. Patent Mo. 4,875,838 assigned to the
assignee of the present invention.
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2063$88
2
It is known in the field of compressors to
use an orbiting piston member to compress fluid.
The disadvantages of these are the complex
mechanisms used to create the orbiting motion. ~In
one prior art example of an orbiting piston
~w'~w w ~ compressor, it is known to use a conventional"
Oldham ring assembly to prevent rotation, but
there were no means for achieving axial and radial
compliance of the orbiting piston within the
cylinder housing.
The present invention is directed to
overcoming the aforementioned disadvantages
wherein it is desired to provide an axial force
and radial force upon the orbiting cylindrical
piston to facilitate sealing and prevent leakage
between the cylindrical piston and cylinder
housing.
The present invention overcomes the
disadvantages of above described prior art
compressors, by providing axial compliance and
"' n~ ~ ' ~~ radial compliance, to resist the tendency of "t'he "' ' ~,~~,,.,
orbiting piston to separate both axially and
radially during compressor operation. The use of
a cylindrical piston member makes the compressor
easy to manufacture. The orbiting rotation of the
cylindrical piston reduces friction between metal
to metal contact surfaces within the compressor.
Generally the present invention provides a
compressor comprising a cylinder and a cylindrical
piston. The piston is caused to orbit by means of
an Oldham ring disposed between the piston and
drive mechanism. A swing link assembly connected
to the drive causes the orbiting piston to
radially comply with the cylinder. Axial
compliance between the piston and cylinder is
. _ ., , ,~, . -,
2~6~888
3
accomplished by suction and discharge pressure
regions inside the compressor housing.
More specifically, the invention provides, in
one form thereof, an annular piston orbiting
within the cylinder. This orbiting piston mounted
on an orbiting plate creates an additional pocket
for the compression of refrigerant.
In one aspect of the invention, two vanes,
.~ ., ".,. ,.. ,: -.,.. ~lidable ~ in radial slots in the cylinder housing,
cause sealing of the compression chambers and
separation between suction and discharge pressure
sections.
In an alternative eiment, there is a
single slidable vane, through the annular orbiting
piston, which separates the compression chambers
into suction and discharge pressure sections. The
slidabie vane slides against an area of the
cylinder walls that has a specific radius to
prevent seizing.
In another alternative embodiment, the
orbiting piston member is not annular, but solid;
and orbits within a cylinder without a fixed .
center section. This configuration creates a
single compression chamber which can be separated
by a single vane into suction and discharge
pressure sections.
A advantage of the instant invention is the
capacity for radial compliance of the piston along
the cylinder side walls. This enhances sealing and
improves pumping ratios.
A further advantage of scroll compressors is
that the present invention minimizes overturning
moments on the orbiting piston and allows for a
more stable compressor.
Yet another advantage of the compressor of
the present invention is that axial compliance of
2f 38$8
,'', 4 _
the orbiting r tot~ar~l a fixed r is
accomplished effectively without excessive leakage
between the discharge pressure region and suction
pressure region of the compressor.
Anathsr advantage of the present invention is
the provision of a simple, reliable, inexpensive,
and easily aanufactursd camprsssor.
Preferred embodiments of the present invention
will now be described, byway of example only, with
reference to the attached figures, wherein:
FIG. 1 is a transverse cross-sectional view
showing the compressor of the present invention.
FIG. 2 is a partially sectioned top view of
the compressor of the present invention,
particularly showing the discharge valve asse~ly.
FIG. 3 is a fragmentary longitudinal
sectional view of the compressor of the present
invention.
FIG. 4 is an enlarged frag~asntary cross
sectional view of the discharge valve area of the
compressor.
FIG. 5 is a side alsvational view of the
Oldham ring.
FIG. 6 is a top plan view of the fixed
cylinder housing.
FIG. 7 is a fragmentary longitudinal
sectional view of the compressor of Figure 1.
FIG. 8 is a cross-sectional view of an
_., , aiternativs eabc~diment of the present invention
featuring a single vane.
FIG. 9 is an enlarged cross-sectional view of
an alternative aabadias~r~t of the present invention
featuring a single orbiting piston.
Referring now to FIGS. 1 and 3, there is
shown a hermetically sealed compressor to having a
housing 12. The housing Z2 has a top cover plate
14, a central portion 16, and a bottom portion
(not shown): ~tithin h~rasstically sealed housing
12 is an electric motor (not shown) that provides
2063888
the power to turn crankshaft 20. Crankshaft 20 is
of conventional construction including an axial
oil passageway 22 to allow passage of lubricating
oil from an oil sump (not shown) to compressor
5 mechanism 24.
A compressor mechanism 24 is enclosed within
housing 12 and generally comprises a cylinder
housing assembly 26, an orbiting piston assembly
28 and a main bearing frame member 30. As shown
in FiG. 3, the cylinder housing assembly 26
includes a top member 32, having an end wall 33,
to which is fastened a generally circular center
cylinder member 34, and an annular outer cylinder
member 36, by means of screws 38. Between fixed
center cylinder member 34 and annular fixed outer
cylinder member 36, there is an annular
compression space 40 where the orbiting piston
assembly 28 interfits. Fixed center cylinder
member 34 has a recessed bottom portion 42 and
void 44 which functions as an oil reservoir for
orbiting piston assembly 28. Annular fixed outer
cylinder member 36 has an inner wall 46 that
defines the walls of the compression chamber.
Fixed cylinder housing assembly 26 is fastened by
means of a plurality of screws 48 to top cover 14.
An annular seal element 50 is disposed between
fixed outer cylinder member 36 and the top surface
51 of main bearing frame meatier 30 to seal against
discharge pressures.
The orbiting piston assembly 28 includes a
generally flat orbiting plate 52 having a mounting
surface 54 and a drive surface 56. Annular
orbiting piston member 58 has an inside wall 60,
outside wall 62, and end face 63. Annular
orbiting piston member 58 is fastened into a
annular groove 64 in mounting surface 54 of the
D
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- orbiting plate 52 by a plurality of screws 66, as
", " "" " ~, , shown in ,FIG. 6, although it could be connected by ",,", , ,
welding, brazing, or integrally formed on orbiting
plate 52. An axial oil passageway 68 extends
through orbiting plate 52 allowing oil flow
between the axial oil passage 22 in crankshaft 20
and void 44 in fixed center cylinder member 34. A
radial oil passageway (not shown), within orbiting
plate 52 permits oil flow to the mounting surface
54 radially outside of orbiting piston member 58.
The orbiting annular piston 58 is interfit into
the space 40 between the fixed center cylinder
member 34 and fixed outer cylinder member 36.
Orbiting plate 52 is larger than the annular
opening 40 in fixed outer cylinder member 36 and
slides on bottom surface 70 of fixed outer
,, ,~,:,~.. . .cylinder ,member 36. An annular seal 71 is opexably ; , , . , .
,";,,
interfit between bottom surface 70 of fixed outer
cylinder member 36 and orbiting plate 52 to seal
between discharge pressure and suction pressure
regions.
An Oldham ring 72 is intermediate the
orbiting plate 52 and the main bearing frame,
member 30. As shown in FIG. 5, Oldham ring 72 is
of conventional construction with two pairs of
keys 74, and 76. Upwardly facing key pair 74
interfit and slide within grooves 78 and 80 in
drive surface 56 of orbiting plate 52. Downwardly
facing key pair 76 slide and interfit within
groove 82 in main bearing member 30. Oldham ring
72 prevents the orbiting piston assembly 28 from
rotating about its own axis.
FIG 6. shows annular groove 84 where an
annular seal element 86 is disposed to seal
between orbiting plate 52 and thrust surface 88 of
main bearing frame member 30. The drive surface
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56 of orbiting plate 52 forms a hub 90 into which
crank mechanism 92 connected to crankshaft 20 is
received. The crank mechanism 92 is a conventional
swing link assembly including a cylindrical roller
94 and an eccentric crank pin 96, whereby roller
94 is eccentrically journalled about eccentric
crank pin 96. Roller 94 is journalled for
rotation within hub 90 by means of sleeve bearing
91, which is press fit into hub 90. Sleeve
bearing 91 is preferably a steel backed bronze
bushing. Further, hollow roll pin 95 is press fit
into bore 97 of roller 94 and extends into pocket
99 crankshift 20 so that roller 94 is restrained
from pivoting completely about crankpin 96. This
restrant against pivoting is used primarily during
assembly to keep roller 94 within a range of
positions to assure easy assembly. Below this
crank mechanism 92 is a counterweight 98 attached
to crankshaft 20.
The interfitting of the orbiting piston
member 58 within t:he space between the fixed
center cylinder member 34 and inner wall 46 of
fixed outer cylinder member 36 creates an inner
pocket 102 and outer pocket 104 that compress
refrigerant when t:he orbiting piston member 58 is
orbited.
As shown in FIG. 1, the fixed center cylinder
34 includes a radial slot 106 receiving a biasing
means, such as a spring 108, and an inner vane 110
which separates the inner pocket 102 into a
discharge pressure section 112 and a suction
pressure section 114. Also included on the top of
the fixed center cylinder member 34 is an inner
discharge port 116. On the opposite side of where
inner vane 110 seals against the orbiting piston
member 58 is an outer vane 118. Outer vane 118 is
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disposed within a radial slot 120 in the fixed
outer cylinder member 36 and biased toward the
orbiting piston member 58 by means of a spring
122. Outer vane 118 separates outer pocket 104
into a discharge pressure section 124 and a
suction pressure section 126. Received in the
fixed outer cylinder member 36 next to the outer
vane 118 is an outer discharge port 128.
Now referring to FIGS. 2 and 4, above the
inner and outer discharge ports 118 and 128, is a
discharge valve assembly 130 consisting of an
inner discharge valve 132 over inner discharge
passageway 134 and inner discharge port 116, and
an outer discharge valve 136 over outer discharge
passageway 138 and out.r discharge port 128. Valve
retainers 140 and 142 are connected to the top
housing 14 over both discharge valves to prevent
overflexing of valves 132 and 136. A discharge
chamber 144 is provided above discharge valve
assembly 130 to allow refrigerant at discharge
pressure to flog away from valve assembly 13o and
into the compressor housing 12. From the housing
12, compressed fluid may exit through discharge
tube 146, (FIG. 3) to the cond~nser of
refrigeration system (not shown). Through top
housing 14 is a suction intake port 148
communicating with outer fluid pocket 104. The
annular orbiting piston member 58 has a plurality
of openings 150 through which refrigerant at
suction pressure may flow to inner pocket 114.
The operation of the compressor, as indicated
in the embodiment in FIG. 1, occurs as the
compressor motor (not shown), rotates crankshaft
20. Crankshaft 20 and crank mechanism 82 cause
the orbiting plate 52 to rotate. The Oldham ring
72 between the orbiting plate 52 and main bearing
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9
member 30 prevent rotation and instead cause the
orbiting plats 52 to orbit. The annular orbiting
piston member 58 orbits within the space between
the fixed center cylinder member 34 and fixed
outer cylinder member 36.
The orbiting of the annular orbiting piston
member 58 causes both the inner vans 110 and outer
vane 118 to move radially within their radial
slots 106 and 120. Since the vanes are shorter
than the radial slots 106 and 120 and are biased
toward the orbiting piston 58 by springs 108 and
122, the vanes seal against the orbiting piston
58. The movement of piston member 58, inner vane
110 and outer vane 118, create pockets of changing
volume when the orbiting piston 58 orbits.
Refrigerant is drawn first into outer pocket
104 by direct suction through suction inlet port
148. Since inner pocket 114 is connected through
openings 150 to outer pocket 104, refrigerant also
2o is suctioned into inner pocket 114. As the
orbiting piston 58 orbits, the point of contact
with the fixed annular cylinder member wall 46
moves past the suction inlet 152. This
effectively creates at least one substantially
closed chamber 154. As the piston 58 continues to
orbit the chamber 154 moves in front of the point
of contact and contracts in size due to the
geometry of the orbiting piston 58, inner wall 46
and moving inner and outer vanes 110 and 118. The
compressed fluid is s~cpelled through the discharge
valves 132 and 136 on each aids of the orbiting
piston 58. Compressed fluid at discharge pressure
can now fill the discharge chamber 144, compressor
housing 12, and exit though discharge tube 146.
The compressor 10 and housing 12 are designed to
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.... .,..,. _ .. . .i ~ . ii.n. , i~ a ~..~~u,.iN
be at substantially discharge pressure during
operation.
Radial co~tpliance of the orbiting piston 58
is accomplished by means of the swing-link
5 assembly on the crank mechanism 92. The mechanism
92 forces the orbiting piston 58 to seal in the
radial direction against the inner wall 46 of the
fixed outer cylinder member 36. Upon compressor
operation the cylindrical roller 94 upon pin 95
10 and crankpin 96 is thrown radialiy outward,
thereby pressing orbiting piston 58 radially
outward.
The axial compliance of the orbiting piston
,,, , "., . .. .., 58 occurs. as the comgressor begins operation...
Discharge pressure on drive surface 56, and
suction pressure on mounting surface 54 force
orbiting plate 52 axially upward toward top member
32. Annular orbiting piston member 58 attached to
orbiting plate 52 is also
forced axially upward, causing end face 63 to
sealingly engage with end wall 33 of top member
32. Discharge pressure behind orbiting plate 52
causes sealing between inner pocket i02 and outer
pocket 104 at the point where end face 63 meets
end wall 33. Outer pocket 104 is separated from
the discharge pressure of compressor housing 12 by
means of annular seal 71 an annular seal 86.
An alternative embodiment, as shown in FIG.
comprises fixed center cylinder member 34 and
fixed outer cylinder member 36 separated by an
annular orbiting piston member 58. The piston
member is driven by the same mechanism as the
previous embodiment. In this embodiment, a single
vane 156 is slidingly disposed through the annular
orbiting piston member 58 sealing against the
annular orbiting piston member 58, fixed center
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11
cylinder member 34 and fixed outer cylinder member
~~, .. a;,~.... , . . .... 36 . In this' embodiment, the single vane 156 ~~ .
slides back and forth in the annular orbiting
piston member 58 while the annular orbiting piston
member 58 orbits.
The distance began the fixed center
cylinder member 34 and the fixed outer cylinder
member is not constant. The area 158 were the
single vane 158 sliding seals against the fixed
outer cylinder member 35 has a different radius to
prevent the vane 156 from seining against the
fixed outer cylinder member 36 as it tilts back
and forth during compressor operation.
Specifically the area 158 has the same radius as
the fixed center cylinder member 34 so the
distance between the cylinders is constant for a
'"' ' " ~- ~ ~ distance ' equal to the stroke of the compressor .
The length of the vane 156 is equal to the
distance between the two cylinder members 34 and
36 at area 158.
In the alternative embodiment of FIG. 9,
there is a fixed outer cylinder member 36 and a
cylindrical orbiting piston 160 received in a
larger cylindrical void 162 in the fixed outer
cylinder member 36. A discharge port 164 and an
intake port 166 separated by a single vane 168.
The single vane 168 is slidingly disposed within a
radial slot 170 and biased toward the orbiting
piston 160 by means of a spring 172. Piston
member 160 is driven by the same mechanism as is
the previous embodiment.
.",.K., ._. ,. _ i , ~, ,~. , , "-w~rr
It will be appreciated that the foregoing
description of various embodiments of the
invention is presented by way of illustration only
and not by way of any limitation, and that various
alternatives and modifications may be made to the
2~~63888
12
- illustrated embodiment without departing from the
spirit and scope of the invention.
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